#include<bits/stdc++.h>
using namespace std;

int main(){
    long double target;
    cin>>target;
    long double m = 2.0;
    long double sum = 0.0;
    int cnt = 0;
    if(target <= 2){
        cout<<1<<endl;
    }
    while(1){
        sum = sum + m*0.98;
        cnt++;
        if(sum >= target){
            break;
        }
    }
    cout<<cnt<<endl;



    return 0;
}